Welding Digest

One of the easiest ways to improve productivity with filler metals is to use less of them, and to achieve that goal, all companies need to do is to follow the welding procedure specification (WPS) for weld size. Problems typically occur because untrained welders think more metal makes the weld stronger. A chain is only as strong as its weakest link (and a weld is only as strong as its smallest leg), so overwelding accomplishes nothing positive.

Certified Welding Inspectors, supervisors, and quality assurance/quality control personnel can use overwelding as an educational opportunity.

However, even if you do not have to comply with a WPS, using extra filler metal and the associated shielding gas add needless costs, and the impact multiplies when considering the cost of wasted time. Reclaiming 45 minutes of production time might be more important than saving $50 to $100 or more on the example joint. Given that welders are needed, the industry cannot afford to waste time it does not have to spare. If it helps, buy every welder a gauge set and teach them how to measure their own welds; tell them they must grind off the excess deposits themselves.

Overwelding also has other financial and technical ramifications. To start, it distorts the true cost of welding, affecting bid accuracy and job profitability. The longer welding time associated with adding excess weld material increases the amount of heat introduced into the base metal, potentially leading to distortion. Larger welds can introduce greater amounts of residual stress, which might increase the likelihood of cracking or other failures, and adding excess weld material can unnecessarily increase the weight of a structure.

Calculating Costs

Free online welding calculators provide a fast and easy way to calculate the cost of changing welding variables. For example, consider welding amperage. Because welding slower is easier, welders with less skill might be tempted to reduce amperage. Consider a WPS for a 5/16-in. fillet weld with an E71T-1 electrode that specifies 300 A and 28–30 V. When using a 0.052-in.-diameter electrode, that yields a deposition rate of 9.21 lb/hour. If the operator reduces amperage to 275, deposition goes down to 8.07 lb/hour and arc-on time increases to 124 minutes from 108 minutes.

Continuing the 5/16-in. fillet weld example, this weld can — and probably should — be made with a 1/16-in.-diameter electrode (see lead photo). Stepping up to the next size wire (without changing amperage) increases the deposition rate to 10.17 lb/hour and reduces arc-on time to 98 minutes. If the WPS permits, substantially more improvements are possible. Welding at 325 A increases the deposition rate to 11.63 lb/hour and reduces arc-on time to 86 minutes.

However, some steel fabrication shops resist using a 1/16-in. gas shielded flux cored arc welding (FCAW-G) electrode because faster travel speeds require more operator skill. Introduce larger-diameter wires in a practice environment. Have an application expert on hand to coach the welders on good mechanics, such as travel speed, to control bead size, gun angles, and proper electrode extension.

Larger-diameter electrodes also provide other benefits. First, because they fill the joint faster, they reduce heat input and can mitigate distortion. Second, larger wires make it easier to ensure good sidewall fusion without excess gun manipulation. If you observe operators weaving the gun when they should be making stringer beads or having issues with intermittent sidewall fusion, those are good signs you need to increase wire diameter. Third, larger-diameter wires may cost less per pound, and using a bulk wire drum really lowers the cost per pound.

More Considerations

Fabricators often choose FCAW-G electrodes because they handle mill scale and rust better than solid wires, enable all-position welding, and have a broader operating range compared to gas metal arc welding (GMAW), which makes it easier for operators to fine-tune the arc.

However, they only have a deposition efficiency of 80 to 90%, require time for slag removal, and generate more fumes compared to solid or metal-cored electrodes. If the steel can be shot blasted clean, using a solid or metal-cored wire in the spray or pulsed spray transfer mode could lower the total welding cost. Deposition rates are at least comparable, and eliminating slag and reducing fumes could tip the balance. Metal-cored electrodes also add the benefit of better sidewall fusion.

To enable all-position welding with solid or metal-cored electrodes, switch to a pulsed GMAW (GMAW-P) output (Figure 1). The historic knock on GMAW-P was that the equipment was too complex, but that is no longer the case. Today’s welding systems with synergic capabilities program with literal push-button simplicity in about 20 seconds. Moreover, synergic controls eliminate the guesswork associated with fine-tuning. To weld faster or hotter, simply increase wire feed speed. To weld slower or cooler, decrease wire feed speed. Going one step further, adding limit and lock functions can ensure WPS compliance.

Parting Thoughts

Calculating the true cost of welding requires considering the financial impact of many variables, and the cost per pound of filler metal is possibly the least important among them. Work with application experts who offer a holistic view and offer the resources required to help you decide the best options for your company. That could be providing operator training to reduce overwelding and defects, changing wire diameter, or using a different process. Or it could be knowing where to introduce mechanized or automated solutions. After all, there is more than one way to make a 5/16-in. fillet weld.

This article was written by John Hartnett (product manager at ESAB) for the American Welding Society.